1. Field of the Invention
The present invention concerns a free-flowing heavy duty granular laundry detergent composition containing high levels of nonionic surfactant and describes a process for manufacturing these materials.
2. The Prior Art
Most granular detergents are produced by spray drying. This process involves slurrying of detergent components and spray atomization in a high temperature air stream. Volatile materials, such as nonionic surfactants, are emitted into the air when processed by this method with the other detergent components. This volatilization problem, manifested by discharge of dense "blue" smoke from the spray tower, is referred to as "pluming". Air pollution standards limit the opacity of the plume. Consequently, it is necessary to limit the capacity of the spray tower, or in extreme instances, discontinue operation.
Inclusion of the nonionic surfactants in the spray dry process also is hazardous. Increased incidences of fire and explosion result. Auto-oxidation or process upset are blamed for such occurrences.
In an attempt to avoid the problems caused by spray drying, considerable developmental effort has focused on post-dosing. In post-dosing, the nonionic surfactant is added to the product after the spray drying operation. Usually, this method works well only for surfactants that are normally solid. Yet, it is the liquid and semi-liquid nonionics whose inclusion is more desirable in detergent compositions. Post-dosing of spray dried base with liquid or semi-liquid surfactant, in amounts sufficient to provide satisfactory wash performance, generally, results in poor flowing aesthetically displeasing products. Accordingly, the amount of liquid and semi-solid surfactant that may be employed in the detergent formulation is severely limited. This limitation is disadvantageous, since, for heavy duty laundry detergents, it is desirable to have large amounts of nonionic surfactant present.
In an attempt to solve this problem, inorganic silicates have been formulated with the spray dried powders to absorb the nonionic liquids. However, an extreme dust explosion hazard exists with these formulations. Further, the silicate method is usually only useful for low and moderate loadings of nonionic surfactant. At higher levels, product crispness and compaction deteriorate. Moreover, these silicates only function as process aids; they have no significant cleaning activity.
Therefore, a need exists for a composition which substantially overcomes the problem of free-flowability in highly loaded nonionic detergents while decreasing the attendant fire, explosion and pollution hazards.